The invention relates to the insulation of an adsorber comprising several parallel-passage contactors and to the use of this same adsorber.
Adsorption is a physical phenomenon that is being used more and more industrially for separating or purifying gaseous flows.
For example, adsorption is used conventionally to dry various gaseous flows, in particular air or natural gas for producing hydrogen, for producing oxygen and/or nitrogen from atmospheric air, and for capturing numerous constituents of various effluents before use thereof in a downstream method or venting thereof as VOCs, nitrogen oxides, mercury, etc.
The methods used are either of the lost load type or regeneratable. The regeneration takes place either by pressure reduction or by temperature increase. It is also possible to couple these two effects. PSA (pressure swing adsorption), TSA (temperature swing adsorption) and PTSA (pressure temperature swing adsorption) are spoken of respectively.
When the regeneration of a PSA takes place under vacuum, the abbreviation VSA (vacuum swing adsorption) is generally used.
The present invention concerns in particular TSAs.
The adsorbent used is generally in the form of particles with which an adsorber is filled. These particles may be in the form of granules, sticks, balls or crushed material. The characteristic dimensions of these particles generally range from 0.5 mm to 5 mm.
The smallest particles improve the absorption kinetics and thereby the efficacy of the method but on the other hand they create significant pressure drops on the fluid phase.
Conventional axial cylinders of adsorbents in the form of balls (ascending or descending circulation of fluid) use thermal insulation between the beds of balls and the surrounding environment.
On a small cylinder, typically with a diameter of less than 2 m, use is made rather of external insulation attached to the external barrel of the cylinder, of the glass wool or cellular glass or polyurethane foam insulation type: this insulation is not very effective since in the phase of regeneration heating of the cylinder, some of the thermal energy is used to heat the metal of the cylinder, requiring compensating for the heat loss in oversizing the regeneration rate.
On a large cylinder, typically with a diameter greater than 2 m, internal insulation is used: this must mechanically be able to contain the beds of balls of adsorbents, not promoting the creation of a preferential gas passage (outside the bed of adsorbents), and be able to withstand any compression/decompression cycles between adsorption and regeneration. Conventionally use is made of a system of single or double layers of gas that serve as an insulating cushion, since the layer of air remains immobile. These layers, relatively efficient in terms of insulation, are difficult to implement and are relatively expensive.
Starting from there, one problem that is posed is providing adsorbents having better insulation, for functioning in TSA.